1. Field of the Invention
This invention relates to a beam scanner for use in laser printer, bar code reader and other applications.
2. Brief Description of the Prior Art
The conventional beam scanner is illustrated in FIG. 10.
In this scanner, the light beam l.sub.3 emergent from a light source is incident on a polygonal mirror 21 and as the mirror 21 is rotated by a motor 22. The direction of a reflection light beam l.sub.4 emergent from the polygonal mirror 21 is varied for scanning. The reference numerals 23 and 24 indicate cylindrical lenses and the numeral 25 indicates a scanning condenser 25.
The above prior art beam scanner has the following disadvantages.
(a) The component parts of the scanner are fairly large and particularly the polygonal mirror 21 and motor 22 impose limitations on overall size reduction. PA1 (b) The polygonal mirror 21 has a plurality of sequentially switchable effective reflective surfaces 21a and because all of the reflective surfaces 21a must reflect the light beam l.sub.4 in a uniform way, they must be equivalent in workmanship but the manufacture of such a polygonal mirror calls for high skill and cost. PA1 (c) As the scanning angle of the light beam l.sub.4 is fixed by the angle which each reflective surface 21a makes with the center of the polygonal mirror 21, the scanning angle cannot be altered. PA1 (d) Because the polygonal mirror 21 is always rotated in a given direction, the scanning direction of light beam l.sub.4 is limited to only one direction, i.e. from right to left or vice versa.
Having been accomplished to overcome the above disadvantages, this invention has as its primary object to provide a beam scanner which is capable of reciprocally scanning in two directions.
Other objects and advantages of the invention will become apparent as the following description proceeds.